Telephone system



May 12, 1931. J. 1. BELLAMY 1,804,822

TELEPHONE SYSTEM Original Filed June 15. 1928 g II I :2. 65 Q: n IE 1 Li s m 5} z *1 r l3 i 1 a L J IrFeTiT:1T-'

' Jahn-LBaZZgmH Patented May 12, 1931 JOHN i. BELLAMY, on nnoonnrnnn,rumors, essrenon T0 RESERVE nonmne com- PANY, or KANSASCITY, srrssoonr,A CORPORATION on DELAWARE .rnnnenonn 's-Ys'rmvr Application filedJuney1328, Seria1*l\'|"o.285,530. Renewed May-24, 1930.

T he present invention relates to telephone systems in jgenerah'thatisconcerned more particularly with telephone systems using non-numericalswitching apparatus; andthe 5 main object is the production of: new'andimprovedarrangements 1 whereby the operation ofth'e so-calledplunger-type secondary, non- :numerical' line switches is rendered moresatisfactory.

The present invention hasbeen applied to secondary lineswitches of theplunger type used in airautomatictelephone system bei tween one level ofthe banks of aigroup of automatic'selectors anda. groupioi' trunk linesdivided intosub groupsas regards the level 111- question and each subgroup has accessto ten trunlrsextending to secondary line 4 switchesinseveral groups, each secondary line switch group being controlled byaseparate master switch andhavingiaccess to a separate sub group of tenoutgoingvtrunk lines. g

Although arrangements as outlined above have eenemployed commerciallyformany years; and-have proven highly satisfactory, an outstanding detecthasEbeen present. This'defect lies in thearrangements provided forrendering the incoming trunks busy to the remaining secondarylines-witches of v a sub group when one of them is seized. The resultisthat one or more additional'line switches are often seized and perhapsoperated before the remainingtrunksare made busy to the selectedswitches having access to them, "This'resu'lts in lost calls owing tothe tact that two switches often seize thesame trunk. andowing tothe'fact thatthe second connection has often released by the time themaster switch finds an idle trunk in casethe last seized secondaryswitchwas seized too late to be operated before the battery potential isremoved from the so-ca'lled openhe no further calls should be permittedto come I into the secondary group because. such line switch: takes thelast remaining idle trunk.

v Keeping 'in mind the defects Outlined above, the specific. object Ofthe presentin- 1 ventien is the productionof suitable circuitarrangements 'for rendermgallthe rema1naingidle trunk lines busy in asecondary sub groupwhen one of thenris seizeduntilthe seized lineswitchhas operated zand the master switch has located a new-idle trunkline.

Accordingly, the circuit arrangements have .-placin'g:oi i a groundpotential onaany: one: of

them seized by a selector renders the; entire sub group busy,arrangements being provided 'forremoving the busy condition only afterthe seized line switch has operatedand the master switch has foundanother idle trunk line. By this arrangement, if the: trunk seized isthe last-idle one in a group, the masterswitch; is unable to findanother idle trunk line and the .busy condition-is maintain-ed ontheremainwing idle trunk incoming lines until such time as anotheroutgoing trunk: line becomes idle and is preselected. It: illbeunderstood of ;.'course,. that while one subgroup of trunkli-nesis,=-busy the callsare routedaby the contain idletrunk lines.

' Referring now, to the drawings comprising :Figs-l and 2, Fig. l'showsa trunk line comprising conductors 2,3, and 4, and leading from thebanksof selectors (not shown) tothe secondary line switch SLS. --TherepeaterR, which is one ct -the ten-repeaterstowhich the, secondary line7 switch SLSzhas access :in common with other secondary line switches,

is shown interposed between .theline switch I banks and the outgoingconduotorsg27and 28, according tostandard practice. A. portionzof :tliemaster sswitch which :presides (,OVGI thesaidgroup'conta-ining thesecondary line switchSLS has been shown in the lowerpartt ot thedrawing,as well as the control groupof relays common I to the sub :group (,ofline switches. The secondary, line-switchisarranged through thecooperation 'ofrelays; 5 end 6 to r apply. gr und. potentiallto;releas,sel-ectors into such other subgroups as may 1 trunk conductor 3 uponthe release of the connection for a short interval so as to maintain thetrunk line guarded during the restoration of the plunger arm therealignment of the plunger so as to permit the use of the socalled selfaligning plungers, which plungers are immediately returned to thecontrol of the master switch without waiting for the master switch to beadvanced to where it will pick themu'p again.

' The invention having been described generally, a detailed descriptionof the operation of the'apparatus shown will now be given.

For this purpose it will be assumed that the master switch is standingin the position shown in the drawingwith the trunk line extending to therepeater R preselected and that the idle trunk comprising conductors 24and extending to the secondary line switch SLS is seized by a selector.When the seizure is made, the calling subscribers loop is extended andplaced across conductors 2 and 4 n the usual manner and ground potentialis applied by the seizing selector to release-trunk conductor 3.Conductor 3is normally con- I nected through contacts of relays 5 and 6to guard conductor 39, which is common, as

indicated. to all theline switches of the sub 7 group. Therefore, theplacing of ground -potential on conductor 3 extends a ground potentialto the similar conductor of each idle line' switch of the sub group, aseach idle line switch has its release trunk conductor connected to thecommon guard conductor 39 in the same way as the trunk shown.

In order to maintain the guarding potential applied to conductor 39, thecommon relay 34' in the control group energizes over conductor 39 andlocks ground on conductor 39 at its'upper contacts through contacts ofrelays 32 and33, the slow acting relay 33 being normally energizedthrough contacts of relay 34. Relay 34 opens the circuit of the slowacting relay 33, but relay 33 remains operated for a substantialinterval, the function'of this'relay being such that it is not requiredto fall back on every call, as it is provided for a special condition tobe hereinafter explained.

' Responsive to the extension of the sub- "scribers loop to the lineconductors 2 and 4,

ductor 4 through the lower armature of relay 5. Upon operating, relay 5looks itself relay 5 whose upper winding is connected to conductor2energizes over the calling line from the ground potential supplied toconi to release trunk conductor 3 at its inner lower armature and itdisconnects release-trunk conductor 3 from the common guard conductor 39at its inner upper armature and closes a circuit from the groundedconductor 3 through the pull-down winding of the line switch magnet 7 tobattery by way of the open-main conductor 38, through normally result ofthe operation of relay 5 it disconnects its upper winding and groundfrom conductors 2 and 4, and closes a circuit for the slow-releasingrelay 6, which operates and prepares a guarding circuit for the trunkline.

As a result of the extension of theconnection to the repeater R, linerelay thereof operates over conductors 21 and 24 from the subscribersloop and closes a circuit for release relay 26 which operates and placesa ground potential on conductor 22 which extends back to release trunkconductor 3 of the secondary line switch so as to maintain the secondaryline switch and the other apparatus of the connection, including theseizing selector, in an opera-ted condition. As the further result ofthe operation of relay 25 of the repeater R, a bridge is placed acrossthe outgoing conductors 27 and 28 including the right-hand repeatingcoil windings, preparing the switch (usually a selector) to whichthetrunk line extends in the distant office for operation in the usualmanner.

As a result of the depression of spring 10 of the line switch SLS, whenthe line switch is operated as above described, 'a ground potential isplaced on test conductor 23, rendering the trunk line busy to the masterswitch, with the result that start relay of the master switch operatesthrough test wiper 37, and closes a circuit at its lower armature fordriving the master switch away from the busy trunk in search of an idleone. At its upper armature, relay 35 removes battery from the open-mainconductor and places a ground potential thereon, closing a circuit forrelay 31 of the common control group, which relay operates and closes anew locking circuit for relay 34 at its upper armature, at the same timeoperating relay 32 at its lowerv armature to open the initial lockingcircuit.

When the master switch finds an idle trunk as evidenced by the factthatno ground potential is encountered on the test conductor of such trunkline by test Wiper 37, start relay 35 falls back and stops the operationof the master switch by opening its lower contacts. Itremoves the groundpotential from the open main conductor 38 and replaces a Q 1 tialhasbeen removed from the common coninseam battery "potential thereon, where'upo'n 'relay 31 of the common grou'p falls back an'd removes theground otential from thelocking ireuitef reiay 3 l-"and from the guardcon- 1 d-uctoi 39, whereupon I relay '34 falls back and opens a furtherI point in its locking. circuit, at the same timereclosing thecircuitofthe slow acting relayf33, which relay is usually i'ng -the' test.Relay 31 also opens thercircuit 'pares the initial 1 locking circuit ofrelay The relative" adjustment o'frelays 32 and 34- issuchthat relay 3falls back "and opens afurther; point in its locking cireuit 'beforere-' -layi32 can fall backandreclosethe initial loeki ng circuit ofrelay 34.

The master switch has-now selected an otheridletrunk line and the groundpotensductor39-so that other calls may benow handle d throughthesaidygroup. It will be understood-of course, that theoperation ofpreselectingwanother idle trunk andagain -contacts;;of line relay-"ofthe repeater R over conductors-27-and-28 to set the said switchesi'irthe distant office in the usual manner.

lVhen the receiver isreplaced on the calling telephone, relay 25 fallsback andjproa armature, whereupon the seizing selector and.

other switching apparatus included in the connect-ion release, and relay5' ofthe second- I aryline sWitch'SLS'falls back. Uponso doing, relay 5,at its inner upper armature,

closes :a circuit through the operated armature of slow-acting relay 6toground, reapplyinga-guarding potential to conductor 3 so as to'preverita reseizure ofthe secondary switch during the restoration "andrealign 'ment of the'plunger thereof. After sufficient time is allowedfor this operation the slow acting relay 6: falls back,in res'pon'seto;

-its-circuit being opened at the-lower armature of; relay 5, andreconnects the conductor 3-. to the common guard conductor 39.

5 Referring again to i the repeater R- and to is a chain circuit for thestop'relay- 36 in the master switch including contacts of relay 26 r andsimilar contacts'of other relays'suchgas stop relay 36of the inastenswitch only when all trunk :linesa cessible to theline switches cuitofrelay 34'.

I of the sub group" are 'busy, merely to stop usenecessary drain on "theexchange battery. The-busy' condition is maintained on a sec- 'ondarygroup because test wiper 3? of 2 the master switch does not encounteranun- Jguarded test contact. Therefore relay 35 is still inanoperatedcondition unless a large:

0 number of trunks have been passed' over durmaintain d operated, withtheresult that 'relays 3,1 and3 l- 'are inaintained operated toRegarding the'utility off'the slow acting frelay 33,'it'may' befpointedout that aground "potential'is likely to 'be su'pplied accidentally toone ofthe release trunk conductors, suchas the release trunk conductor 3of the I secondary line switch SLS, causing relay 34:

tolockup'and hold. a busy condition on the entire sub groupeven afterthe original ac:

cuit of which opened upon the operation'of relay 34, the locking circuitofirelay '34 and the busy circuitover conductor 39 isshortly openedremoving the guarding potential ate relay '33 to again preparethelocking cir- Referring now tol3ig 2'it will be apparent that thesecondary line switch SLS shown therein'is similar in every respectexcept that no relay corresponding to relay 6 of Fig. 1 is prov'i'dedand that the'back contact of the inner upper-armature ofrelay 5leads'directly" to the common guard ,conductor instead ofthroughcontacts of'a relaysimilar to relay Gas in Fig. 1. This modification is.for use of course wherever the self-aligning plunger'mare not'requiredand therefore not What is claimed 1. In a telep'hon'e trunking system, aplu ;rality of incoming trunks each terminating in'a'pres'electingswitching mechanism, a less- "er' plurality of outgoing'trunksaccessible in common to all said mechanisms, means for making busy allidleincomingtrunks whenany incoming trunk is taken for use, n1eans forthereafter operatingthe switching mech- -anism in which theseized' trunkterminates, rn'ea-ns common to all said pr'ese'lecting switchingmechanisms forpreselecting another out {going trunk, and means formaintainingthe busy condition'on' the incoming trunks'until the masterswitch it will be noticed that there said preselecting means haspreselected another. trunk.

' 2. In a telephone'system wherein a plurality of non-numericalswitching mechanisms are accessible to automaticswitchingappara"tus,-an"d are presided over bya master switch arrangedfto cause allidle "nonmumerical SWitClll11'gmechanisms controlled-thereby to lmaintain ground potential on guard con- 7 ductor 39.

froin therelease trunk conductor and permitting relay 34.- to fallbackagain andreoperpreselect the same idle outgoing trunk, means artificallybusy all idle switching mechanisms before the said seized mechanismisoperated and for maintaining them busy to said automatic switchingapparatus until the said operation of the master switch is performed.

3. In a telephone system wherein automatic switching apparatus hasaccess to non-numerical switches governed by a master switch arranged topreselect an idle one of a plurality of trunks accessible to thenon-numerical switches and to presele'ct another idle trunk when thepreselected one Is taken for use, means responsive to the seizure of oneof said non-numerical switches for making all of them busysimultaneously and for maintaining the busy condition until thepreselected trunk has beentaken for use by the seizedswitch and themaster switch has operated to preselect another trunk.

4. In a telephone system wherein automatic switching apparatus hasaccess to' non numerical switches governed by a matter switch arrangedto preselect an idle one of a plurality of trunks accessible to thenon-,

1 numerical switches and'to preselect another idle trunk when thepreselected one is taken for use, means responsive to the seizure of oneof-said non-numerical switches-for making all of them busy and formaintaining the busy condition until the preselected trunk has beentaken for use by the seized switch and the master switch has operated topreselect another trunk, said means including a self locking relayoperated over the seized trunk line and unlocked responsive to theoperation of the master switch.

5. In a telephone trunking system, a plurality of trunks, meansresponsive to a seiz ure of oneof said trunks for making all idle onesbusy, and means including a progressively movable testing device commonto said trunks for removing the busy condition from all of them that areidle. 7

6. In a telephone'system, a plurality of incoming trunks, a plurality ofoutgoing trunks, switching mechanism for seizing incoming trunks,switching mechanism for connecting seized incoming trunks to idleoutgoing trunks, and means common to said incoming trunks and controlledover any one of them for making all idle incoming trunks artificiallybusy whenever any one of them is seized. V

7. Ina telephone system, a plurality of in-. coming trunks, a pluralitya of outgoing trunks, switching mechanism for seizing incoming trunks,switching mechanism for con-.

necting seized incoming trunks to idle outgoing trunks, means common tosaid incoming trunks and controlled over any one of them for making allidle incoming trunks artificially busy whenever any one of them isseized, and means including a timing device common to all said incomingtrunks for rendering idle the artificially busy trunks.

8. In a telephone system, a group of trunk lines, means common to saidlines for placing an artificial busy condition on all idle" trunk lines,and means including a timing device common to said trunk lines forremoving the said artificial busy condition.

9. In a telephone trunking system, a plus rality of incoming trunks eachterminating in a preselecting switching mechanism, a lesser plurality ofoutgoing trunks accessible in common to all said mechanisms, means formaking busy all idle incoming trunks when for thereafter operating theswitching mechanism in which the seized'trunk terminates,

means for maintaining the busy condition on the incoming trunks untilanother trunk is preselected, and means, automatically effective toremove the busy condition at the end of a predetermined time in case thelastnamed switching mechanism fails to operate.

10. In a switching system, a line, an automatic switch arranged toextend said line, a line relay connected to said line and arranged to beenergized thereover, an oper ating circuit for said switch controlled bysaid line relay, a release trunk conductor included in said line, aself-locking circuitfor said line relay including said release trunkconductor, means external to said lineswitch for applying potential'tosaid release trunk conductor before the lineswitch is operated toprepare the said locking circuit for the line relay, and means externalto said switch for removing the locking potential from said releasetrunk conductor when the connection set up through the switch is to bebroken for deenergizing said line relay to permit said switch torelease.

11. In a' switching system, an incoming line terminating in alineswitch, said line in- .cluding a line conductor and a releaseconductor, means for applying potential to said release conductor andfor operating said line relay in a circuit over the line conductor ofsaid line, contacts on said line relay for closing a self-lockingcircuit for itself to said release conductor and for opening its linecircuit, and additional contacts on said line relay for closing anoperating circuit for said lineswitch.

12. In combination, a line incoming to a lineswitch arranged to extendthe line, said line comprising a line conductor and a release conductor,means for applying a potential to said release conductor and for closinga circuit over the line conductor for said any incoming trunk is takenfor use, means line relay, and contacts on said line relay for closing aself-locking circuit over said re lease conductor, for opening its linecircuit, and for closing an operating circuit for said lineswitch overthe release conductor.

13. In a switching system, an automatic switch, a line incoming to saidswitch including a line conductor and a release trunk con ductor, meansincluding a line relay in said switch for operating the switchimmediately responsive to current flow over the incoming line conductor,and means for maintaining said automatic switch operated responsive tofurther current flow over the incoming release trunk conductor.

14. In a switching system, a preselecting lineswitch accessible to anautomatic switch by way of a trunk line including a line conductor and arelease trunk conductor, means for operating said automatic switch toextend a connection to the preselecting switch by way of said trunkline, means for operating the preselecting switch responsive to currentflow over the line conductor of the trunk line incoming thereto, andmeans for maintaining said preselecting switch operated by means ofcurrent flow over the re lease trunk conductor of the incoming trunkline.

15. In a switching system, a non-numerical automatic switch, a trunkline incoming to said switch comprising a line conductor and a releasetrunk conductor, means for extend ing a connection to said switch by wayof the said conductors of said trunk line and for setting up a currentflow over the line conductor of the incoming trunk line and for applyinga holding potential to the release trunk conductor oi the incoming trunkline, means in said non-numerical switch responsive onlyto current flowover both-said incoming conductors for operating the nonnumericalswitch, and a circuit for holding said switch operated including theincoming release trunk conductor of said trunk line.

16. In a switching system, a plunger lineswitch having access to aplurality of lines, means for preselecting one of said lines, a trunkline incoming to said switchhaving a line conductor and a releaseconductor, means including an automatic switch forextending a connectionto the lineswitch by way of said conductors, means for operating thelineswitch responsive to current flow over the line conductor incomingthereto, and a holding circuit for both of said switches completed oversaid release trunk conductor.

17. In a switching system, a plurality of non-numerical switches havingaccess to trunk lines, a line incoming to each of said switchescomprising a line conductor and a release conductor, a separateconductor multipling all of said release conductors together, a linerelay in each of said switches, means for taking any one of saidswitches for use oyerithe incomin line. thereof; and for sett ng up; a;current; I

contacts on said line relay for'closing an op,- er'atmg circuit fortheswitch andfor dis:

connecting the release conductor. otthe assov ciatedincoming line fromthecommoncohductor;

l8: Ina switching system, a, plurality ottrnnlr lines accessible to anautomatic switch,

each oiirsaidytrunk lines including a line conductor and aj releaseconductor, connec tions multiplmgall ofsaid release conductors:

together, a line relay -ineachof said trunk lines responsive to currentflow overthe as-1 iow over the line con; 1 1 ductorot the incommgl ne,said line relay being respons ve to sald current flow, and;

s ciated line conductor when the trunk line l is taken for use by, saidautomatic switch,

and contactsjon saidline relay for, discone. necting the associatedreleaseconductor, from the common conductor,

19. In a, switching system, ,a plura-lity of automatic switches, aseparate trunklineine coming to ea'ch switch, each trunk; line. in

cluding aline conductonanda release conductor, all; of said releaseconductors-being;

normally connectedtogether so that the: ap; plication ofguardingpotential toone ofthem;

results in an application of guardingpotential to all or" them, meansfor taking anyone of said trunk lines for use, means responsive theretofor operating the switchin which the;

seizedline terminates and for disconnecting;

the associatedireleaseconductor from the other release conductors andfor .closinga holdi.

mg circuit for the associated switch over the release conductor,meansfor subsequent ly opening the] holding circuit to permit theoperated switch tov release, and means responsive thereto for applying aguarding potential to said release conductor.

20'. In a switching system, a plurality of automatic switches, aseparate trunk line incoming to each switch, each trunk line ine eludinga line conductor and a release con erated switch to release, meansresponsive thereto for applying a guarding potential to said releaseconductor, and means for subsequentiy removing said guarding potentialand for reconnecting said release conductor to the release conductors ofthe other trunk lines.

21. In a non-numerical switch having a line conductor and a releaseconductor incoming thereto, a line relay operative over the lineconductor, and an operating circuit for said switch including saidrelease conductor and closed responsive to the-energization of the linerelay;

22. In combination, -a non-numerical switch, a line conductor and arelease trunk conductor incoming thereto from a preceding automaticswitch, and a magnet responsive to operate said non-numerical switchdepending upon the closure of a line circuit over the incoming line andthe application of a potential to said release-trunk conductor when thesaid preceding switch is operated.

23. In a telephone system, a line, an automatic switch and means forcontrolling the same to extend said line to an idle trunk line,

a preselecting secondary plunger lineswitch terminating said trunk line,means controlled over a talking conductor of said trunk line foroperating said lineswitch when the trunk line is seized by said firstswitch, a release trunk conductor extending between said switches, meansin said automatic switch for applying potential momentarily to saidrelease trunk conductor and for removing it 7 after an interval, andmeans controlled through said secondary switch for applying potential tosaid releasetrunk conductor for maintaining the first switch in operatedposition after the potentialhas been removed from the said release trunkconductor at said automatic switch.

In witness whereof, I'hereunto subscribe my name this 13th day of June,A. D; 1928.

JOHN I. BELLAMY.

